Scanning apparatus



` July 9, 1940.

L. C. McNUTT SCANNING APPARATUS- 2 Sheets-Sheet 1 Original Filed May 20, 1938 |NvEN`ToR Louls c. McNuT-r BY U Tl. MA A ORNEY- July 9, 1940. L c. McNUTT SCANNING ,APrARATUs 2 sheets-,Sheet 2 original Filed May' 2o, 1958 hmmm om ww.

JQQQQQQUQQQ INVENToR Y Lows c. McNuT-r BY vwl-m.,

QQQQQQQQQQQQQQ ATTORNEY malanni, 9, 1940 UNITED STATES PATENT OFFICE K 2,206,969 y scANNiNG APPARATUS :mais c. McNutt, scotch Plains, N. J., assignor to M. W. Kellogg Co., New York,vN. Ys., a corporation of Delaware original application May 2o, 193s, serial No.

209,153. Divided and this application April 2 9, 1939, Serial No. 270,739

z claims. (c1. 2664-23) 10 severe service conditions, is highly important. This is especially true of composite metal, i. e.,

metal that includes a base such asns'teel to which is united a comparatively thin protective lining of alloy of special properties. The bond between the alloy andthe base is seldom perfect and it' is not unusual to iind areas df substantial size in an apparently perfect plate, or sheet, at which there is either no bond at all or the bond is so poor that it may fail in the' intended service.

It is not possible to determine, by examinationof test pieces, the existence ,of the unbonded4 areas in composite metal or the existence of subsurface defects such as laminations, slag and impurity inclusions, gas pockets, etc., in Vunlined metal. Satisfactory results can only be obtained by an examination of the whole metal body. 'I'he prior art does not disclosel a simple and inexpensive method for effecting such an examination.'

v It is an object of this invention to provide appropriate apparatus for carrying out in pra'ctice, a novel method for inspecting bodies to determine the existence of sub-surface defects,

which apparatus is characterized by its simplicity,

eillciency and low cost of operation. The further objects and advantages 'of the in-1 vention will berbetter appreciated from a con` sideraton of the `following description taken -with the accompanying drawings, in which Y Fig. 1 is a side elevation of Va present preferred 40 form of novel apparatus for practicing the method of this invention, and Fig. 2 is a plan view, with aportion broken out, oi the apparatus of Figi 1. Metal whether in the cast or worked condition, is seldom free from lsub-surface defects. This isn true of composite metal, i. e., metal that gener' ally is made up of a. steel base towhich is united a comparatively thin coating 'of alloy of special properties, asareas will appear in which there is either no bond at all between thesteel base and the alloy coating 'or the bond is of imperfect c'xharacter.4 s 1 It becomes necessary, as for instance, when composite metal vis used as the material for pres- 'u sure vessels, such as the pressure -ves'sels of the petroleum refining, chemical and similar processing arts, that in use are subjected to extreme temperature and pressure conditions, to determine the 'sub-surface character of the metal so that it may be classified as acceptable or not ac ceptable for the service. It also becomes necessary, as' for instance in the circumstances just 'above alluded to, to locate sub-surface defects so that these .may be removed and the metal repaired.

The novel method of this invention is a complete solution ofthe inspection problem since it not only makes it possible to determine the existence of sub-surface defects but leaves a permanent record of their location and outline on the surface of the metal. Furthermore, the novel method is -a simple one and can be carried out quickly and easily with a minimum of apparatus.

In the present preferred manner of practicing the novel method a source of heat is progressed at a uniform rate over the surface of the metal body to be inspected so that each increment of the surface has applied to it a like quantity of heat at a like temperature. `If the bodyof' metal is of homogeneous-character each increment of the heated surface will attain the same maxlmum temperature. If, however, the body is not homogeneous but includes sub-surface defects, as for instance, in composite metaLareas inthe zone of union between the alloy covering and the steel base in which the bond is non-existent or is imperfect, the heat transfer rate through these areas is less than through the remainder of the zone of union so that the surface of the metal body overlying these areasattains a higher temperature than the rest .of the surface. This dif# ference of temperature, 'and hence the Vexistence lof sub-surface defects may be indicatedl in various ways.

Thus. for instance, a plurality oi spaced temperature responsive devices, positioned across the heated band, may be progressed with the source of heat, 'but in back of it. The devices may serve to merely indicate temperature, in which case an operator will mark the high temperature areas,

or the devices may be of the recording type so tions. A I accomplish this desirable result by employing a heat source which is capable of supplyingy large quantities of heat at extremely high temwell as the outline of the sub-surface imperfecperatures and progress the source over the surface to be examined at such a rate that the areas nent and characteristic discoloration upon cool- 'ing to ordinary temperature.

The heat source may be an oxygen-hydrocarbon ame, an oxygenhydrogen flame, an .electrical resistance, an electric arc discharge between substantially non-consumable electrodes,etc. At present, I prefer to employ a ame and particularly an oxygenacetylene ame. -To render the rmethod more practical it is preferable to employ a plurality of sources at .one time, the sources being properly spaced to uniformly heat a comparatively wide band of the surface, as. wide as several feet or more depending on the size of the metal body to be inspected. Y

` By using a heat source of the character just set forth, not only do the portions of the surface above imperfections attain higher `temperatures Y than those below in which no imperfections occur but they may be made to attain temperatures high enough to render them visible. By choosing a proper frate of progression of the source, the areas above the imperfections may be heated to a dull red heat, or higher, without raising the temperature of the metal of the rest of the surface to temperatures sufficiently high to materially affect its properties and characteristics. Thus, heat treated metal may be inspected without materially affecting the properties developed by the heat treatment.

Upon cooling, ,the` a-reas above the imperfections retain a color, usually blue, due to the lm of oxide formed thereon. From numerous tests y I have found that the colored areas are immediately above the imperfections and, furthermore,l

.that they have substantially the identical pattern. The oxide coloring is a permanent record of thedefects and may be used for comparison against a standard and, furthermore, is a great help in repairing the metal body.

To assure a true record it is advisable to remove all scale and other foreign matter from the surface of the body before the 'heat source is passed over it. This can be conveniently done by sand blasting.` When the oxygen-acetylene flame is used I have also found it desirable at times to preheat the whole plate'lightly to remove all moisture from the surface as at times Water produce stains which may be confused with the spots indicating imperfections.

The method may be employed in the determination of sub-surface imperfections located at various distances below the surface. By choosing a heat source of proper capacity and intensity and progressing the source over the surface at theproper rate, imperfections Vnear the l surface only; as little as a few hundredths of an inch, will be indicated, or Aall imperfections from adjacent the surface to a depth of one-half inch or more will be indicated. 'I'he limit of penetra;- tion cannot be accurately expressed as it depends on many factors such as the heat capacity of the `metal, the heat transfer rate, the amount of heat yforth in the description of the apparatus, illus- -determined depth. After theV source' is .chosen that will give the proper penetration the size imperfections that it lwill indicate will be deter-o mined by the rate at' which the source is progressed over the work.l Thus, one rate will indid cate` all imperfections in the depth examined while a faster rate will only indicate the larger imperfections.

In the inspection of composite metal, having an alloy lining of V64 ofl an inch in thickness I have been able with one speed of travel of the heat source to indicate all imperfections as small as 1/64 inch' in diameter, and less, to a depth oi' 1A of an inch and by increasing the speed of travel of the heat source over the,surface I have been able to indicate to the same depth onlythose imperfections having an average diameter of inch'or more.

Further details of the novel method will be set trated in the accompanying drawings, which is especially suited for carrying out the novel method.

The apparatus includes a metal frame I0, made up of side pieces II and I2, end pieces I3, and a platform Il. 'I'he parts of the frame may be made of steel plate and joined together in any suitable way,- as by welding.

A shaft I5 is supported in bearings carried by pieces II and I2 adjacent end piece I3. One end of shaft I5 is connected to a speed indicating device I6 which is preferably arranged to indicate speed of travel in convenient units as, for instance, feet per minute.

On shaft I5 is fastened a traction wheel I'I .I

which serves to move vthe vehicle along its path. Wheel I`| is provided with a. periphery of rubber lor other non-skid material I8 to prevent slippage.-

of the wheel-relativeto the metal body so that a uniform rate of travel maybe obtained and ac- 4| motor 2|. Gear I9 is mounted for free rotation u on shaft I5 and has attached thereto one half of jaw clutch 22.` uThe other half of jaw clutch 22 is splined on shaft I5. A pin 23, mounted eccentrically on rod 2l that extends through end piece I3, projects into a groove 25 in the splined y Ahalf of' jaw clutch 22. By rotating rod 23, y'through handle 26, the halves of jaw clutch 22 may .be brought into and out of engagement. Thus, by opening the halves of jaw-clutch 22 wheel II may be made to rotate independently 5 of motor. 20 and the apparatus may bequickly pushed about at will by means'of handle 21 that is attached to platform- Il. v MotorZI is bolted to a plate 28, which in turn is welded to standards .2S that are bolted to 6 platform I4. Motor 2| includes a speed changing controlV 30 by means of which the speed of rotation of motor 2 I and 4consequently the speed of rotation of wheel I1 may be varied atwill.

Current for the ener'glzation of motor 2| is supa 'plied through cable 3|. Cable 3| passes through a control box 32 and a switch of the usual construction, not shown. The control switch for cable 3| is opened and closedby themanipulation of handle 33. Handle 33 also operates valves 7 hereinafter to be referred to.

A pair of shaft 34 are supported for rotation in aplatform Il adjacent the forward end of frame Il. To the lower ,end of. each of shafts 34 is fastened an axel 3i upon which a guide wheeli shaft 42 wheels 36 are oriented as-desired to.

36 is mounted. Gui'dewheels 36 are each provided with a hardened and sharpened periphery to enable them to bite into the plate over which the apparatus is progressed to facilitate the steering of the apparatus. together by means of levers 31, 38 and 39 so that a rotary movement of oneshaft 34 produces a like rotary movement of the other shaft 34. At the upper end of one of shafts 34 is carried a worm wheel 40 that'en'gages a, worm 4| carried by shaft 42. Shaft 42 terminates in a wheel 43 that is provided with .a handle 44. By rotating steer the apparatus. p

A shaft 45 passes through side pieces 1| and I2 adjacent the forward end of frame I0. Shaft 45 is held against axial movement by set collars 46. On each end of shaft 45 is mounted a bearing 41 that is held against axial movement by set collars .48. .Crosswise to bearing 41 is attached a bearing 49 whichsupports shaft 58 for rotation therein. -Shaft 56 is held against axial movement by set collars 5I. Each ofshaft 50 support a torch member 52. Torch members 52 are also each supported by a pair of casters 53 equi-spaced from shaft 50. By reason of the .arrangement just described each of torch members 52 is free to move as'required to maintain a has screwed into it, in communication with the central bore, a mixing chamber 55 provided with a Y-shaped top. One branch of the Y is connected through a vflexible hose to a valve 56, the

other branch is similarly connected to valve 51. Valves 56 are on manifold 58 and valves 51 on manifold 59. Manifold 58 'connects with line 60 through a valve located in control box 32 and manifold 59 connects with line 6l through a valve also located in -control box 32. The valves lust mentioned, and the electrical switch previously mentioned are so arranged that by throwing handle 33 in one direction the valves will be opened and the switch closed and by throwing handle 33 inthe opposite direction the valves will be closed and the switch opened. By means of this arrangement the flames cannot be ignited witnoiit simmtaneousiy initiating the progression of the apparatus over the work, nor cani the:

progressione! the apparatus'be stopped without simultaneously .shutting ff the flames. Thus, the apparatus will always be in motion when the flames are burning so that no damage can be done to the metal inspected by reason of an overlong contact with the high intensity ames.

Shafts 34 are connected The free end of pipe 62 terminates in a small burner tip 64 that servesas a pilot flame for the ignition of the names of -torch members 52.

A pressure gage 463 is carried by pipe62. A pipe pressure cylinder through a flexible line to line 6|.

I claim:

1. In apparatus of the character described, a frame, means-for driving said frame over the surface lof a workpiece, means for steering said frame over the workpiece, an axis of rotation defining support member carried by said frame and' disposed transversely of the longitudinal axis of said frame, a member supported by said axis defining member` for substantially free rotation about the defined axis,` a second support member rotatable with said supported member and defining a second axis parallel to the longitudinal axis of said frame, means supported by said second support member for substantially free rotation about the second dened axis, a torch member carried by said supported means and movable therewith, and means attached to said torch member and equispaced from said supported means adapted to bear on the surface of the workpiece as the frame and torch member yare moved thereover, whereby said torch member is adapted to rotate about said defined axes to maintain a predetermined spacing with -regard to the surface of the workpiece beneath it.

2.,In` apparatus of the character described, a frame, controllable means for driving said frame at a desiredrate and in a desired path overthe surface of a workpiece, a shaft supported `in said frame disposed transversely of the line of travel 'of said frame, a cross-bearing member having one bearing positioned for substantially free rotation on said shaft, a second shaft positioned for substantially free rotation in the second bearing of said cross-bearing member, a torch member attached to said second shaft, said torch member including a body portion extending laterally on both sides of the pointv of attachment to said second shaft, and spacing means attached to the body portion of said torch member'A and equi-spaced from the point of attachment of said torch member and said second shaft `adapted to contact the surface of the workpiece to maintain said torch member at a predetermined distance from the surface of the workpiece beneath it.

Louis c. ucNU'rr. 

